Under the Sea Party Ideas for Kids & Adults

Dive into a world of shimmering blues, sandy textures, and ocean-inspired magic with an Under the Sea–themed celebration. This theme offers endless possibilities—whether you want playful mermaid fun for kids or a breezy coastal vibe for an adult gathering. Think pearly accents, seashells, soft aqua tones, and the soothing feel of seaside escape.

Below is your complete guide to creating a celebration that feels enchanting, immersive, and beautifully oceanic.

🐚 Under the Sea Fun for Kids

Kids adore anything that feels adventurous, sparkly, and full of imaginative play—and this underwater theme checks every box.

Treasure Hunt with “Pearls” & Seashells

Transform your space into a sandy treasure cove. Hide plastic pearls, seashells, or gold coins around the yard or party area. Give kids small buckets or treasure bags and let them search for undersea riches. This activity is exciting, simple to prep, and keeps kids entertained for a long time.

Make-Your-Own Jellyfish Craft

Using paper bowls, ribbons, tissue paper, and foam stickers, kids can create their own floating jellyfish friends. It’s colorful, whimsical, and easy for all ages. Hang the finished jellyfish from a string so kids can “swim” them around the party.

Mermaid or Shark Photo Backdrop

Photo areas are always a hit. Set up a backdrop featuring waves, coral, mermaid tails, or shark fins. Kids love taking photos with themed props—and parents love having adorable memories to keep.

Kids’ Party Favors

Send little guests home with ocean treasures such as:

• Mini treasure chests filled with stickers

• Seashell necklaces

• Mermaid or ocean creature bookmarks

  
  

Mighty Pen Designs can create custom stickers, bookmark designs, and personalized labels to match your theme.

🌴 Coastal-Inspired Activities for Adults

For adults, an Under the Sea theme can feel breezy, refreshing, and delightfully coastal when paired with the right activities.

Ocean-Inspired Wine Tasting or Cocktail Flight

Offer a selection of ocean- or coast-inspired drinks—think citrus spritzers, sea-salt margaritas, or tropical blends. Label each sample with fun nautical names or tasting notes for a charming touch.

Seashell Candle-Making Station

Set up a simple candle-making station with natural soy wax, seashell molds, ocean-scented oils, and soft blue or sandy-toned dyes. Guests can create their own mini coastal candles to take home.

Coastal Trivia or Nautical Charades

Lighthearted and entertaining, trivia and charades are perfect for groups. Include questions or prompts about sea creatures, famous coastal landmarks, beach movies, and ocean myths. It adds a splash of laughter and friendly competition.

Adult Party Favors

Offer favors that feel thoughtful and perfectly on-theme:

• Sea salt scrubs

• Coastal-themed magnets

• Mini candles in scents like ocean breeze, driftwood, or sea salt

  
  

Mighty Pen Designs can help create custom labels, magnets, and packaging to bring these favors together beautifully.

🌊 Bringing Your Under the Sea Party Together

The beauty of this theme lies in the atmosphere you create—soft ocean hues, iridescent details, seashells, netting, twinkle lights, and subtle coastal textures. Use blues, aquas, pearlescent whites, and touches of coral to evoke that dreamy underwater feel. Scatter shells, pearls, and starfish across tables, or drape fishing netting over signs and displays for instant ocean charm.

Whether you’re planning a mermaid-inspired kids’ party or a seaside escape for adults, an Under the Sea theme brings joy, creativity, and a sense of wonder to every moment.

If you’d like custom party favors, labels, bookmark designs, or under-the-sea extras, Mighty Pen Designs can help bring your vision to life with personalized touches that make your celebration unforgettable.

Let’s Connect!

Questions or want to chat party ideas? Email me at julia@mightypendesigns.com or DM me on Instagram @mightypendesigns!